CN101644792A - Polaroid sheet, manufacturing method thereof and liquid crystal display device - Google Patents

Abstract

The present invention relates to a polarizing plate, a method for producing the same, and a liquid crystal display device using the polarizing plate. The polarizer includes a polarizing film (51) in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film and the dichroic dye is oriented; A first protective layer (52) composed of a cured product of a curable composition of an active energy ray curable compound; and a thermoplastic resin film laminated on the other side of the polarizing film (51) via an adhesive layer (54) The second protective layer (53).

Description

Polarizing plate, manufacturing method thereof, and liquid crystal display device

technical field

The present invention relates to a polarizing plate, especially a polarizing plate suitable for use in an in-plane switching (IPS) mode liquid crystal display device, a method for manufacturing the same, and a liquid crystal display device using the polarizing plate that operates in an in-plane switching mode.

Background technique

In recent years, liquid crystal display devices (LCDs) have been used as mobile phones, portable information terminals (personal digital assistants: PDAs), personal computers, televisions and other information devices due to various advantages such as low power consumption, low operating voltage, light weight, and thin shape. The use of display devices is rapidly increasing. With the development of liquid crystal display technology, various modes of liquid crystal display devices have been proposed to gradually eliminate the problems of LCDs such as response speed, contrast ratio, and narrow viewing angle.

As one of the countermeasures for viewing angle compensation, a liquid crystal cell that can essentially expand the viewing angle has been proposed. For example, optically compensated bending (Optically Compensated Bend: OCB) mode, vertical alignment (Vertical Alignment: VA) mode, in-plane switching (In-Plane Switching: IPS) mode, etc. are mentioned. Among them, the IPS mode is a mode in which the alignment state of the liquid crystal molecules is changed by in-plane switching by applying a voltage in a direction parallel to the substrate surface. In the IPS mode, in the state where no voltage is applied, the alignment of the liquid crystal molecules and The substrate planes are parallel, but are not twisted like in the TN mode, but are oriented approximately in the same direction.

The principle of the IPS mode is described according to FIG. 1 and FIG. 2 . FIG. 1 is a schematic cross-sectional view showing a configuration example of an IPS mode liquid crystal display device. 2 is a schematic perspective view showing an example of normally black for explaining the principle of the IPS mode, (A) showing a state when no voltage is applied, and (B) showing a state when a voltage is applied. It should be noted that, in FIG. 2 , each layer is shown spaced apart for easy understanding. In addition, in FIG. 2(B), reference signs are added only to parts that are in a different state from (A), and reference signs are omitted for parts that are in the same state as (A) in order not to obscure the drawing.

A liquid crystal cell 10 serving as the center of an IPS mode liquid crystal display device is composed of upper and lower cell substrates 11 and 12 and a liquid crystal layer 14 sandwiched between these cell substrates. The liquid crystal molecules 15 constituting the liquid crystal layer 14 are aligned substantially parallel to the surfaces of the respective cell substrates 11 and 12 . And above and below the liquid crystal cell 10, the front side polarizing plate 20 and the back side polarizing plate 30 are arranged respectively, so that the light from the backlight 40 arranged outside (the back side) of the liquid crystal cell 10 only The linearly polarized light parallel to the transmission axis of the back-side polarizing plate 30 between the backlight 40 enters the liquid crystal cell 10 . Polarizers generally include polarizing films, protective films, and the like.

In the state shown in FIG. 2(A) where no voltage is applied, the liquid crystal molecules 15 are aligned parallel to the cell substrate surface and in substantially the same direction. In this example, the liquid crystal molecules 15 are aligned in a direction substantially parallel to the light transmission axis 32 of the rear polarizing plate 30 . On one unit substrate (lower substrate in this example) 12, electrodes 13, 13 are arranged in parallel in a comb-like shape. In this state, the linearly polarized light 16 that has passed through the back side polarizing plate 30 passes through the liquid crystal layer 14 in the state where the polarization state is not changed as it is, and the linearly polarized light 17 in the same direction as that at the time of incidence Pass through the unit substrate 11 on the upper side. If the transmission axis 22 of the front side polarizing plate 20 disposed thereon is perpendicular to the light transmission axis 32 of the back side polarizing plate 30, the linearly polarized light 17 that has passed through the upper side unit substrate 11 cannot pass through the front side polarizing plate. 20, becomes display black state.

On the other hand, as shown in FIG. 2(B), when an electric field 18 indicated by a dotted line is applied between the electrodes 13 and 13 arranged in parallel on the cell substrate, the long axes of the liquid crystal molecules 15 are aligned along the electric field 18, The transmission axis 32 of the polarizing plate 30 on the rear side is deviated. As a result, the linearly polarized light 16 that has been incident on the liquid crystal cell 10 changes its polarization state while passing through the liquid crystal layer 14, and becomes elliptically polarized light 17' after passing through the liquid crystal layer 14, generating a light transmission axis capable of passing through the front side polarizer 20. 22 ingredients, thus showing the bright state.

In addition, in FIG. 2 , the example shown is arranged so that the light transmission axis 32 of the back side polarizing plate 30 is approximately parallel to the long axis of the liquid crystal molecule 15, and is arranged so that the front side polarizing plate 20 and the back side polarizing plate 30 The transmission axis of the front side polarizing plate 20 is perpendicular to each other, but even if it is arranged so that the light transmission axis 22 of the front side polarizing plate 20 is approximately parallel to the long axis of the liquid crystal molecule 15, and the light transmission axis of the front side polarizing plate 20 and the back side polarizing plate 30 is arranged so that the The axes are orthogonal, and the same result will be obtained. Mainly, what is necessary is just to arrange|position so that the long axis of the liquid crystal molecule 15 may be substantially parallel to the transmission axis of either polarizer. At this time, the long-axis direction of the liquid crystal molecules 15 does not need to be strictly parallel to the light transmission axis of any one of the polarizers. In order to rotate the liquid crystal molecules 15 in a certain direction when the electric field 18 is applied, it may deviate by a certain angle. , eg by an angle within 10°. In addition, since the light transmission axes of the front side polarizing plate 20 and the back side polarizing plate 30 are arranged so that they are perpendicular to each other, so-called normally black in which a black state is displayed when no voltage is applied and a bright state is displayed when a voltage is applied is often the case. If the transmission axes of the front polarizing plate 20 and the back polarizing plate 30 are arranged in parallel, a so-called normally white state is displayed when no voltage is applied and a black state is displayed when a voltage is applied.

In this way, in the IPS mode, since the liquid crystal molecules are aligned parallel to the substrate surface and aligned in the same direction, the viewing angle characteristics are superior to those in other modes. However, since the triacetyl cellulose film conventionally used as a protective film in a polarizing plate has an in-plane retardation _Re of approximately 5 nm and a film thickness direction retardation R _th of approximately 50 nm, when it is used as a protective film disposed on In a liquid crystal display device with a protective film between the liquid crystal cell and the polarizing film, transmitted light is birefringent, and there is a problem of light leakage during black display.

In order to solve this problem, for example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2006-18245), it is disclosed that a transparent film having a small retardation R _e in the plane and a retardation R _th in the film thickness direction is prepared and used as a protective film in a polarizing plate. technology used.

On the other hand, in order to make the protective film of the polarizing plate thinner, for example, the technique disclosed in Patent Document 2 (Japanese Unexamined Patent Publication No. 2004-245924) is to absorb a dichroic dye on a polyvinyl alcohol-based resin film and A technique in which an uncured epoxy composition is applied to at least one side of a polarizing film on which the dichroic dye is oriented, and then cured to form a protective film. However, for polarizers in which the cured product of the epoxy composition disclosed therein forms a protective film, the durability is insufficient, for example, the shrinkage of the polarizing film under high temperature conditions cannot be sufficiently suppressed, and polarizers with a size exceeding 15 inches In , there are problems such as cracking of the polarizing film.

Contents of the invention

An object of the present invention is to provide a polarizing plate having a small retardation R _e in the plane of a protective layer disposed on the liquid crystal cell side and a retardation R _th in the film thickness direction, and furthermore, a polarizing plate excellent in thinness, light weight and durability, In particular, it is a polarizing plate suitable for use in an in-plane switching (IPS) mode liquid crystal display device and a method for producing the same. In addition, another object of the present invention is to provide a liquid crystal display device using the polarizing plate, particularly a liquid crystal display device operating in an in-plane switching mode.

The present invention provides a polarizing plate comprising: a polarizing film in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film and the dichroic dye is oriented; A first protective layer formed of a cured product of a curable composition of an active energy ray-curable compound, and a second protective layer formed of a thermoplastic resin film are laminated on the other surface of the polarizing film via an adhesive layer.

In the polarizer of the present invention, the curable composition used for forming the first protective layer preferably contains an epoxy-based compound having at least one epoxy group in the molecule as an active energy ray-curable compound, more preferably the ring The oxygen compound has at least one epoxy group bonded to an alicyclic ring.

The curable composition may further contain an oxetane compound as an active energy ray-curable compound. In addition, the curable composition may contain a (meth)acrylic compound having at least one (meth)acryloyloxy group in the molecule as an active energy ray-curable compound.

The first protective layer formed from a cured product of the curable composition preferably has a thickness of 0.1 to 10 μm.

The second protective layer is preferably formed of a cellulose acetate resin film. In addition, the adhesive layer is preferably formed of a cured product of a curable composition containing an active energy ray-curable compound.

The polarizing plate of the present invention may further include an adhesive layer laminated on the surface of the first protective layer opposite to the polarizing film side. The polarizing plate of the present invention is suitable for use in a liquid crystal display device operating in an in-plane switching mode.

In addition, the present invention provides a liquid crystal display device comprising a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, at least one of the pair of polarizing plates is the present invention having the above-mentioned adhesive layer. Polarizer, and bonded on the liquid crystal unit by means of the adhesive layer; the present invention also provides the following liquid crystal display device, that is, equipped with a liquid crystal unit and a pair of polarizers configured on both sides of the liquid crystal unit, the pair of polarizers Each of the sheets was the polarizing plate of the present invention provided with the above-mentioned adhesive layer, and was bonded to the liquid crystal cell via the adhesive layer.

The liquid crystal cell in the liquid crystal display device of the present invention preferably has two substrates and a liquid crystal layer sandwiched between the substrates and oriented substantially parallel to the substrates when no voltage is applied, and operates in an in-plane switching mode.

Furthermore, according to the present invention, there is provided a method for producing a polarizing plate comprising a polarizing film in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film and the dichroic dye is oriented, and a polarizing film laminated on the polarizing film. A first protective layer composed of a cured product of a curable composition containing an active energy ray-curable compound on one side of the polarizing film, and a second protective layer formed of a thermoplastic resin film laminated on the other side of the polarizing film via an adhesive layer. The protective layer, the production method includes the following steps, that is, the coating layer forming step of providing the coating layer of the curable composition on the surface of the substrate, making the coating layer of the curable composition provided on the surface of the substrate A coating layer lamination process of laminating on one side of the polarizing film, a film lamination process of laminating a second protective layer on the other side of the polarizing film via an adhesive, and a curing process of curing the coating layer and the adhesive step, and a substrate removal step for removing the substrate.

In the curing step, the coating layer and the adhesive are preferably cured simultaneously by irradiating active energy rays from the substrate side.

The polarizing plate of the present invention includes a first protective layer having a small in-plane retardation Re and _{a small retardation R th in} the film thickness direction. Therefore, when such a polarizing plate of the present invention is applied to a liquid crystal display device such that the first protective layer is on the liquid crystal cell side, light leakage can be effectively prevented. In addition, by constituting the first protective layer from a cured product of a curable composition, the thickness of the protective layer can be reduced compared with conventional triacetyl cellulose (TAC) films and the like, and therefore thinner and lighter polarizers can be achieved.

Furthermore, according to the method for producing a polarizing plate of the present invention, the polarizing plate according to the present invention can be produced without providing a drying step, and the production process can be simplified.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing a configuration example of an IPS mode liquid crystal display.

2 is a schematic perspective view of a normally black example for explaining the principle of the IPS mode, (A) showing a state when no voltage is applied, and (B) showing a state when a voltage is applied.

FIG. 3 is a schematic cross-sectional view showing a preferred example of a polarizing plate according to the present invention.

Symbol Description

10-liquid crystal unit, 11, 12-unit substrate, 13-electrodes, 14-liquid crystal layer, 15-liquid crystal molecules, 16-linearly polarized light incident on the liquid crystal unit, 17-linearly polarized light after passing through the liquid crystal unit 17'- Elliptically polarized light after passing through the liquid crystal cell, 18-electric field, 20-front side polarizer, 22-transmission axis of the front side polarizer, 30-back side polarizer, 32-transmission axis of the back side polarizer, 40 -Backlight, 50-Polarizer, 51-Polarizing film, 52-First protective layer, 53-Second protective layer, 54-Adhesive layer, 55-Adhesive layer

Detailed ways

<Polarizer>

FIG. 3 is a schematic cross-sectional view showing a preferred example of a polarizing plate according to the present invention. The polarizing plate 50 shown in FIG. 3 includes a polarizing film 51 , a transparent first protective layer 52 laminated on one surface of the polarizing film 51 , and a transparent second protective layer 53 laminated on the other surface. The first protective layer 52 is composed of a cured product of a curable composition containing an active energy ray curable compound. The second protection layer 53 is formed of a thermoplastic resin film, and is pasted on the polarizing film 51 via the adhesive layer 54 . In addition, the polarizing plate 50 has an adhesive layer 55 for bonding to a liquid crystal cell or the like on the outside of the first protective layer 52, that is, on the surface of the first protective layer 52 opposite to the polarizing film 51 side. . Moreover, the polarizing plate of this invention does not need to have an adhesive layer. The polarizing plate of the present invention will be described in detail below.

(polarizing film)

The polarizing film to exhibit the function as a polarizing plate is a polarizing film in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film and the dichroic dye is oriented. The polyvinyl alcohol-based resin constituting the polarizing film is obtained by saponifying polyvinyl acetate-based resin. Examples of polyvinyl acetate-based resins include, in addition to polyvinyl acetate, which is a vinyl acetate homopolymer, copolymers of vinyl acetate and other monomers that can be copolymerized therewith, and the like. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and the like. The saponification degree of polyvinyl alcohol-type resin is about 85-100 mol% normally, Preferably it is 98-100 mol%. The polyvinyl alcohol-based resin may be further modified. For example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. In addition, the degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 10,000.

The film obtained by forming this polyvinyl alcohol-type resin into a film can be used as an original film (original reverse film) of a polarizing film. The method of forming a polyvinyl alcohol-based resin into a film is not particularly limited, and a known method can be used to form a film. The film thickness of the raw film made of polyvinyl alcohol-based resin is not particularly limited, but is, for example, about 10 μm to 150 μm.

A polarizing film is usually produced through the steps of uniaxially stretching an original film made of the above-mentioned polyvinyl alcohol-based resin, dyeing the polyvinyl alcohol-based resin film with a dichroic dye, A step of adsorbing the dichroic dye, a step of treating the polyvinyl alcohol-based resin film having adsorbed the dichroic dye with an aqueous solution of boric acid, and a step of washing with water after the treatment with the aqueous solution of boric acid.

Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with the dyeing, or may be performed after the dyeing. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or may be performed during boric acid treatment. In addition, uniaxial stretching can also be performed in these multiple stages. In the case of uniaxial stretching, uniaxial stretching may be performed between rolls having different peripheral speeds, or uniaxial stretching may be performed using heated rolls. In addition, dry stretching such as stretching in the air may be used, or wet stretching in which stretching is performed in a state of being swollen with a solvent may be used. The draw ratio is usually about 4 to 8 times.

When dyeing a polyvinyl alcohol-type resin film with a dichroic dye, what is necessary is just to immerse a polyvinyl alcohol-type resin film in the aqueous solution containing a dichroic dye, for example. As the dichroic dye, iodine, a dichroic dye, and the like can be used. In addition, the polyvinyl alcohol-based resin film is preferably subjected to a immersion treatment in water before the dyeing treatment.

When using iodine as a dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is generally employed as a dyeing method. The iodine content in this aqueous solution is usually about 0.01 to 0.5 parts by weight with respect to 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 10 parts by weight with respect to 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40° C., and the immersion time (dyeing time) in the aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous dye solution containing a water-soluble dichroic dye is generally employed as a dyeing method. The content of the dichroic dye in the dye aqueous solution is usually about 1×10 ⁻³ to 1×10 ⁻² parts by weight relative to 100 parts by weight of water. The aqueous dye solution may also contain inorganic salts such as sodium sulfate as dyeing aids. The temperature of the dye aqueous solution is usually about 20 to 80° C., and the immersion time (dyeing time) in the dye aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment after dyeing with a dichroic dye is carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. The content of boric acid in the aqueous solution containing boric acid is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight with respect to 100 parts by weight of water. When using iodine as a dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide. The content of potassium iodide in the aqueous solution containing boric acid is usually about 2 to 20 parts by weight, preferably about 5 to 15 parts by weight, based on 100 parts by weight of water. The immersion time in the aqueous solution containing boric acid is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50°C or higher, preferably 50 to 85°C.

The polyvinyl alcohol-type resin film after a boric-acid process is generally given a water washing process. The water washing treatment is performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water at the time of washing with water is usually about 5 to 40° C., and the immersion time is about 2 to 120 seconds. After washing with water, drying treatment was performed to obtain a polarizing film. The drying process can be performed using a hot air dryer or a far-infrared heater. The drying temperature is usually about 40 to 100°C. The drying time is usually about 120 to 600 seconds.

From the above, it was found that a polarizing film in which a dichroic dye is adsorbed on a uniaxially stretched polyvinyl alcohol-based resin film and the dichroic dye is oriented can be produced. The thickness of the polarizing film can be made about 5-40 μm.

(The protective layer)

In the present invention, the first protective layer provided on one surface of the polarizing film as described above is constituted by a cured product of a curable composition containing an active energy ray-curable compound. In addition, the second protective layer provided on the other surface of the polarizing film is formed of a thermoplastic resin film, and the thermoplastic resin film is bonded to the other surface of the polarizing film through an adhesive layer. Hereinafter, the first protective layer and the second protective layer will be described in order. In addition, a curable composition is also called a curable resin composition.

(1) The first protective layer

The first protective layer provided on one surface of the polarizing film is composed of a cured product of a curable composition containing an active energy ray-curable compound as described above. The active energy ray-curable compound refers to a compound curable by irradiation with active energy rays (such as ultraviolet rays, visible light, electron rays, X-rays, etc.). The active energy ray-curable compound may be a cation polymerizable compound or a radical polymerizable compound. Examples of cationic polymerizable compounds include epoxy-based compounds having at least one epoxy group in the molecule (hereinafter sometimes simply referred to as "epoxy-based compounds"), and epoxy-based compounds having at least one oxetane ring in the molecule. oxetane-based compounds (hereinafter sometimes simply referred to as "oxetane-based compounds") and the like. In addition, examples of radically polymerizable compounds include (meth)acrylic compounds having at least one (meth)acryloyloxy group in the molecule (hereinafter sometimes simply referred to as "(meth)acrylic compounds"). )wait. In addition, "(meth)acryloyloxy" means methacryloyloxy or acryloyloxy.

The cured product obtained by irradiating the curable composition containing such an active energy ray-curable compound with active energy ray provides a product that is excellent in transparency, mechanical strength, thermal stability, etc. and defined in the following formula (1). A protective layer _{in which the in-plane retardation value Re of the film (first protective layer) and the retardation value R th in} the film thickness direction of the film defined by the following formula (2) are substantially zero. Here, substantially 0 means that Re is in the range of 0≦R _e ≦20, more preferably 0≦R _e ≦15, and still more preferably 0≦ _{R e} ≦10. In addition, R _th being approximately 0 means a range of |R _th |≤25, more preferably |R _th |≤23, and still more preferably |R _th |≤20.

R _e =(n _x -n _y )×d (1)

R _th = [(n _x +n _y )/2-n _z ]d (2)

Here, n _x : the refractive index in the direction of the in-plane slow axis of the film

n _y : Refractive index in the film's in-plane fast axis direction (direction perpendicular to the slow axis direction)

n _z : Refractive index in the thickness direction of the film

d: Thickness of the film

The first protective layer is constituted by a cured product of a curable composition whose retardation value _Re in the film plane and the retardation value _Rth in the film thickness direction of the film are approximately 0, and the polarizing plate is placed on the side of the first protective layer. When it is bonded to a liquid crystal cell, light leakage at the time of black display of the obtained liquid crystal display device can be effectively prevented. In addition, since the thickness of the protective layer can be reduced, thinner and lighter polarizers and liquid crystal display devices can be realized.

In addition, the protective layer laminated on the polarizing film is preferably optically transparent, so the haze value of the first protective layer is preferably 0.5% or less, more preferably 0.3% or less, further preferably 0.1% or less. When the haze value exceeds 0.5%, light is scattered, so the transmittance decreases.

The above-mentioned curable composition preferably contains at least an epoxy-based compound as the above-mentioned active energy ray-curable compound, whereby a protective layer exhibiting good adhesion to a polarizing film can be obtained.

As the above-mentioned epoxy-based compound, it is preferable to use an epoxy-based compound that does not contain an aromatic ring in the molecule as a main component from the viewpoint of weather resistance, refractive index, cationic polymerizability, and the like. Examples of such an epoxy-based compound not containing an aromatic ring in the molecule include a hydrogenated epoxy-based compound, an aliphatic epoxy-based compound, an alicyclic epoxy-based compound, and the like.

The hydrogenated epoxy-based compound can be obtained by selectively hydrogenating an aromatic epoxy-based compound under pressure in the presence of a catalyst. As the aromatic epoxy compound, for example, bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; Novolac type epoxy resins such as epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolac epoxy resin; glycidyl ether of tetrahydroxydiphenylmethane, glycidyl ether of tetrahydroxybenzophenone, cyclic Polyfunctional epoxy resins such as oxidized polyvinyl phenol, etc. Among them, glycidyl ether of hydrogenated bisphenol A is preferably used as the hydrogenated epoxy compound.

Examples of the aliphatic epoxy compound include polyglycidyl ethers of aliphatic polyhydric alcohols and alkylene oxide adducts thereof. More specifically, diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane Ether, diglycidyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, one or more kinds of alkylene epoxides ( Ethylene oxide, propylene oxide), polyglycidyl ethers of polyether polyols, etc.

In addition, the term "alicyclic epoxy compound" refers to an epoxy compound having at least one epoxy group bonded to an alicyclic ring. The "epoxy group bonded to the alicyclic ring" has a structure represented by the following formula. In the formula, m is an integer of 2-5.

Therefore, an alicyclic epoxy compound is a compound which has at least one structure represented by the said formula in a molecule|numerator. More specifically, a compound obtained by removing one or more hydrogens in (CH ₂ ) _m in the above formula and other chemical structures can be used as an alicyclic epoxy compound. One or more hydrogens in (CH ₂ ) _m may be appropriately substituted with linear alkyl groups such as methyl and ethyl.

Among the above epoxy-based compounds, preferred are alicyclic epoxy-based compounds, that is, compounds in which at least one epoxy group is bonded to an alicyclic ring, especially, a compound having an oxabicyclohexane ring ( In the above formula, m=3) and epoxy-based compounds of oxabicyclohexane (in the above formula, m=4), because the cured product has a high elastic modulus, it is easy to obtain a protective layer with excellent adhesion to the polarizing film. , so it is more preferable to use. Hereinafter, although the structure of the alicyclic epoxy compound used preferably in this invention is illustrated concretely, it is not limited to these compounds.

(a) Epoxycyclohexylmethyl epoxycyclohexane carboxylates shown in the following formula (I):

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.)

(b) Epoxyhexane carboxylate esters of alkanediols represented by the following formula (II):

(In the formula, R ³ and R ⁴ independently represent a hydrogen atom or a linear alkyl group with 1 to 5 carbon atoms, and n represents an integer of 2 to 20.)

(c) Epoxycyclohexylmethyl esters of dicarboxylic acids represented by the following formula (III):

(In the formula, R ⁵ and R ⁶ independently represent a hydrogen atom or a linear alkyl group with 1 to 5 carbon atoms, and p represents an integer of 2 to 20.)

(d) epoxy cyclohexyl methyl ethers of polyethylene glycol shown in the following formula (IV):

(In the formula, R ⁷ and R ⁸ independently represent a hydrogen atom or a linear alkyl group with 1 to 5 carbon atoms, and q represents an integer of 2 to 10.)

(e) epoxy cyclohexyl methyl ethers of alkanediol shown in the following formula (V):

(In the formula, R ⁹ and R ¹⁰ independently represent a hydrogen atom or a linear alkyl group with 1 to 5 carbon atoms, and r represents an integer of 0 to 18.)

(f) Diepoxy triple spiro compounds shown in the following formula (VI):

(In the formula, R ¹¹ and R ¹² independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.)

(g) the diepoxy group single spiro compound shown in the following formula (VII):

(In the formula, R ¹³ and R ¹⁴ independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.)

(h) Vinylcyclohexene diepoxides represented by the following formula (VIII):

(In the formula, ^R15 represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.)

(i) Epoxycyclopentyl ethers represented by the following formula (IX):

(In the formula, ^R16 and ^R17 independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.)

(j) Diepoxy tricyclodecanes represented by the following formula (X):

(In the formula, ^R18 represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.)

Among the alicyclic epoxy-based compounds exemplified above, the following alicyclic epoxy-based compounds are preferably used because they are commercially available or their analogues are relatively easy to obtain.

(A) esterification of 7-oxabicyclo[4.1.0]heptane-3-carboxylic acid and (7-oxa-bicyclo[4.1.0]hept-3-yl)methanol [in the above formula ( In I), the compound of R ¹ =R ² =H]

(B) 4-Methyl-7-oxabicyclo[4.1.0]heptane-3-carboxylic acid and (4-methyl-7-oxa-bicyclo[4.1.0]hept-3-yl ) Esterification product of methanol [compound of R ¹ =4-CH ₃ , R ² =4-CH ₃ in the above formula (I)]

(C) Esterification product of 7-oxabicyclo[4.1.0]heptane-3-carboxylic acid and 1,2-ethanediol [in the above formula (II), R ³ =R ⁴ =H, n = 2 compounds]

(D) Esterification product of (7-oxabicyclo[4.1.0]hept-3-yl)methanol and adipic acid [in the above formula (III), R ⁵ =R ⁶ =H, p=4 compound]

(E) Esterification product of (4-methyl-7-oxabicyclo[4.1.0]hept-3-yl)methanol and adipic acid [in the above formula (III), R ⁵ =4-CH ₃ , R ⁶ =4-CH ₃ , the compound of p=4]

(F) Etherification of (7-oxabicyclo[4.1.0]hept-3-yl)methanol and 1,2-ethanediol [in the above formula (V), R ⁹ =R ¹⁰ =H, Compounds with r=2]

In the present invention, the epoxy-based compound may be used alone or in combination of two or more.

With regard to the curable composition used in the formation of the first protective layer, the epoxy-based compound preferably accounts for 30 to 100% by weight, more preferably 35 to 70% by weight, and still more preferably 40% by weight of the total active energy ray-curable compound. ~60% by weight. When there is little content of an epoxy-type compound, there exists a tendency for the adhesiveness of a polarizing film and a 1st protective layer to fall.

In addition, this curable composition may contain an oxetane-based compound as an active energy ray-curable compound in addition to the above-mentioned epoxy-based compound. By adding the oxetane compound, the viscosity of the curable composition can be reduced and the curing speed can be accelerated.

The oxetane compound is a compound having at least one oxetane ring (four-membered ring ether) in the molecule, for example, 3-ethyl-3-hydroxymethyl oxetane, 1 , 4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, bis[ (3-Ethyl-3-oxetanyl)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, phenol novolac oxetane alkanes etc. These oxetane-based compounds can be easily obtained as commercial products, and for example, "ARON OXETANE OXT-101", "ARON OXETANE OXT-121", and "ARONOXETANE OXT-211" are listed by trade names. , "ARON OXETANE OXT-221", "ARONOXETANE OXT-212" (both manufactured by Toagosei Co., Ltd.), etc. The blending amount of the oxetane compound is not particularly limited, but is usually 30% by weight or less, preferably 10 to 25% by weight, of the total active energy ray-curable compounds.

When the curable composition used for forming the first protective layer contains a cationic polymerizable compound such as an epoxy compound or an oxetane compound, a cationic polymerizable photoinitiator is usually blended into the curable composition. If a cationic polymerization photoinitiator is used, the protective layer can be formed at normal temperature, so it is possible to reduce the need to consider the heat resistance and deformation of the polarizing film due to expansion, and the first protective layer can be formed on the polarizing film with good adhesion. on polarizing film. In addition, since the cationic polymerization photoinitiator acts as a catalyst due to light, even if it is mixed in a curable composition, it is excellent in storage stability and handleability.

Regarding cationic polymerization photoinitiators, cationic species or Lewis acids are generated by the irradiation of active energy rays such as visible light, ultraviolet rays, X-rays, and electron rays, and the polymerization of epoxy-based compounds and/or oxetane-based compounds The substance that starts the reaction. In the present invention, any type of cationic polymerization photoinitiator can be used. If specific examples are given, onium salts such as aromatic diazonium salts, aromatic iodonium salts, and aromatic sulfonium salts, aromatic sulfonium salts, and aromatic sulfonium salts can be used. Iron complexes, etc.

Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

Examples of aromatic iodonium salts include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, bis(4-nonyl) phenyl) iodonium hexafluorophosphate, etc.

Examples of aromatic sulfonium salts include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl) borate, 4,4'-bis (Diphenylsulfonium) diphenylsulfide bishexafluorophosphate, 4,4'-bis[bis(β-hydroxyethoxy)phenylsulfonium]diphenylsulfide bishexafluoroantimonate, 4 , 4'-bis[bis(β-hydroxyethoxy)phenylsulfonium]diphenylsulfide bis-hexafluorophosphate, 7-[bis(p-tolyl)sulfonium]-2-isopropylthioxanthone Hexafluoroantimonate, 7-[bis(p-tolyl)sulfonium]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate, 4-phenylcarbonyl-4'-diphenylsulfonium -Diphenylsulfide hexafluorophosphate, 4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonium-diphenylsulfide hexafluoroantimonate, 4-(p-tert-butylphenyl (ylcarbonyl)-4'-(p-tolyl)sulfonium-diphenylsulfide tetrakis(pentafluorophenyl)borate, etc.

In addition, examples of ferrocene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, Xylene-cyclopentadienyliron(II)-tris(trifluoromethylsulfonyl)methanide, etc.

These cationic polymerization photoinitiators can easily obtain commercially available products. For example, if they are named by trade names respectively, "Kayarad PCI-220" and "Kayarad PCI-620" (the above are provided by Nippon Kayaku Co., Ltd. ), "UVI-6990" (manufactured by Union Carbide), "Adeka Optomer SP-150", "Adeka Optomer SP-170" (the above are manufactured by ADEKA Co., Ltd.), "CI-5102", "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S" (manufactured by Nippon Soda Co., Ltd.), "DPI-101", "DPI-102 ", "DPI-103", "DPI-105", "MPI-103", "MPI-105", "BBI-101", "BBI-102", "BBI-103", "BBI-105", "TPS-101", "TPS-102", "TPS-103", "TPS-105", "MDS-103", "MDS-105", "DTS-102", "DTS-103" (above by Green Chemical Co., Ltd.), "PI-2074" (Rhodia (Rhodia) Co., Ltd.), "UVA CURE 1590" (Daicel-Cytec Co., Ltd.) and the like.

These cationic polymerization photoinitiators may be used individually, respectively, or may mix and use 2 or more types. Among them, especially aromatic sulfonium salts have ultraviolet absorption characteristics even in the wavelength range of 300 nm or more, so they are excellent in curability, and can provide cured products with good mechanical strength and good adhesion with polarizing films, so they are preferably used.

The amount of the cationic polymerization photoinitiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight, relative to 100 parts by weight of the total amount of cationic polymerizable compounds such as epoxy compounds and oxetane compounds. . When the compounding quantity of a cationic polymerization photoinitiator is too small, hardening will become insufficient, and there exists a tendency for mechanical strength and the adhesiveness of a protective layer and a protective film to fall. On the other hand, when the compounding amount of the cationic polymerization photoinitiator is too large, the ionic substance in the cured product increases, so the hygroscopicity of the cured product increases, and the durability of the obtained polarizer may decrease.

In addition, the curable composition used for the formation of the first protective layer preferably contains not only the above-mentioned epoxy-based compound, or epoxy-based compound and oxetane-based compound, but also radically polymerizable (methanol) base) acrylic compound. By using a (meth)acrylic compound in combination, a protective layer having high hardness, excellent mechanical strength, and higher durability can be obtained. Furthermore, it is possible to more easily adjust the viscosity and curing rate of the curable composition, the surface curability of the obtained protective layer, the adhesiveness to the polarizing film, and the like.

Examples of (meth)acrylic compounds include (meth)acrylate monomers having at least one (meth)acryloyloxy group in the molecule, and compounds obtained by reacting two or more functional group-containing compounds. A (meth)acryloyloxy group-containing compound such as a (meth)acrylate oligomer having at least two (meth)acryloyloxy groups in the molecule. These compounds may be used individually, respectively, and may use 2 or more types together. When two or more types are used in combination, two or more (meth)acrylate monomers can be used, and two or more (meth)acrylate oligomers can be used. Of course, the (meth)acrylate monomer can also be used in combination. One or more kinds of and one or more kinds of (meth)acrylate oligomers. In addition, "(meth)acrylate" means acrylate or methacrylate.

Examples of the aforementioned (meth)acrylate monomers include monofunctional (meth)acrylate monomers having one (meth)acryloyloxy group in the molecule, monofunctional (meth)acrylate monomers having two (meth)acryloxy groups in the molecule, ) bifunctional (meth)acrylate monomers of acryloyloxy groups, and polyfunctional (meth)acrylate monomers having three or more (meth)acryloyloxy groups in the molecule.

Specific examples of monofunctional (meth)acrylate monomers include tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate ester, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, (meth)acrylate Base) 2-ethylhexyl acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate ester, phenoxyethyl (meth)acrylate, dihydrobiscyclopentadienyloxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, ethyl carbit (meth)acrylate Alcohol esters, trimethylolpropane mono(meth)acrylate, pentaerythritol mono(meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, etc.

In addition, a carboxyl group-containing (meth)acrylate monomer can also be used as a monofunctional (meth)acrylate monomer. Examples of carboxyl group-containing monofunctional (meth)acrylate monomers include 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, Phthalic acid, carboxyethyl (meth)acrylate, 2-(meth)acryloyloxyethylsuccinic acid, N-(meth)acryloyloxy-N',N'-dicarboxymethyl- p-Phenylenediamine, 4-(meth)acryloyloxyethyltrimellitic acid, and the like.

Typical bifunctional (meth)acrylate monomers include alkylene glycol di(meth)acrylates, polyoxyalkylene glycol di(meth)acrylates, haloalkylene diol di(meth)acrylates, di(meth)acrylates of aliphatic polyols, di(meth)acrylates of hydrogenated dicyclopentadiene or tricyclodecanedialkonol, Di(meth)acrylates of dioxane diol or dioxane dialkanol, di(meth)acrylates of alkylene oxide adducts of bisphenol A or bisphenol F, bisphenol A or Epoxy di(meth)acrylates of bisphenol F and the like are not limited thereto, and various bifunctional (meth)acrylate monomers can be used.

If more specific examples of bifunctional (meth)acrylate monomers are given, there are ethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4 -Butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate ) acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol di(meth)acrylate, di(trimethylol)propane di(meth)acrylate, diethylene glycol di(meth)acrylate ) acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol Di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, silicone di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, 2,2 - Bis[4-(meth)acryloyloxyethoxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxyethoxyethoxyethoxycyclohexyl]propane , Hydrogenated dicyclopentadienyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,3-dioxane-2,5-diyl di(meth)acrylate Ester [alias: dioxanediol di(meth)acrylate], acetal compound of hydroxypivalaldehyde and trimethylolpropane [chemical name: 2-(2-hydroxy-1,1-dimethyl Ethyl)-5-ethyl-5-hydroxymethyl-1,3-dioxane] di(meth)acrylate, tri(hydroxyethyl)isocyanurate di(meth)acrylate wait.

As polyfunctional (meth)acrylate monomers with more than three functions, glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, bis(trimethylol)propane Tri(meth)acrylate, Di(trimethylol)propane tetra(meth)acrylate, Pentaerythritol tri(meth)acrylate, Pentaerythritol tetra(meth)acrylate, Dipentaerythritol tetra(meth)acrylate ester, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate and other poly(meth)acrylates of trifunctional or higher aliphatic polyhydric alcohols, in addition, trifunctional or higher Poly(meth)acrylate of halogenated polyol, tri(meth)acrylate of alkylene oxide adduct of glycerol, tri(meth)acrylic acid of alkylene oxide adduct of trimethylolpropane esters, 1,1,1-tris[(meth)acryloyloxyethoxyethoxy]propane, tris(hydroxyethyl)isocyanurate tri(meth)acrylates, etc.

On the other hand, among (meth)acrylate oligomers, there are urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, epoxy (meth)acrylic acid Ester oligomers, etc.

The urethane (meth)acrylate oligomer is a compound having a urethane bond (-NHCOO-) and at least two (meth)acryloyloxy groups in the molecule. Specifically, it is a urethanized reaction product of a hydroxyl-containing (meth)acrylate monomer and polyisocyanate having at least one (meth)acryloyloxy group and at least one hydroxyl group in the molecule; A urethane compound having an isocyanato group at the end obtained by reacting polyols with polyisocyanate, and having at least one (meth)acryloyloxy group and at least one hydroxyl group in the molecule Urethanization reaction products of (meth)acrylate monomers, etc.

Examples of the hydroxyl group-containing (meth)acrylate monomer used in the urethanization reaction include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ( 2-Hydroxybutyl Methacrylate, 2-Hydroxy-3-Phenoxypropyl (Meth)acrylate, Glyceryl Di(meth)acrylate, Trimethylolpropane Di(meth)acrylate, Pentaerythritol Tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, etc.

Examples of the polyisocyanate to be subjected to the urethanization reaction with the hydroxyl group-containing (meth)acrylate monomer include hexamethylene diisocyanate, lysine diisocyanate, and isophorone diisocyanate. Isocyanates, dicyclohexylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, and diisocyanates obtained by hydrogenating aromatic isocyanates among these diisocyanates (for example, hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, etc.) Di- or tri-isocyanates such as triphenylmethane triisocyanate and dibenzylbenzene triisocyanate, and polyisocyanates obtained by polymerizing the above-mentioned diisocyanates.

In addition, as polyols used to produce urethane compounds having isocyanato groups at their terminals by reaction with polyisocyanate, in addition to aromatic, aliphatic, and alicyclic polyols, it is also possible to use Polyester polyol, polyether polyol, etc. Examples of aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and neopentyl glycol , Trimethylolethane, Trimethylolpropane, Di(trimethylol)propane, Pentaerythritol, Dipentaerythritol, Dimethylolheptane, Dimethylolpropionic Acid, Dimethylolbutyric Acid, Glycerin , hydrogenated bisphenol A, etc.

The polyester polyol can be obtained by the dehydration condensation reaction of the above-mentioned polyols and polyvalent carboxylic acids or their anhydrides. Examples of the polycarboxylic acid or its anhydride include succinic acid (anhydride), adipic acid, maleic acid (anhydride), itaconic acid (anhydride), trimellitic acid (anhydride), and pyromellitic acid (anhydride). , phthalic acid (anhydride), isophthalic acid, terephthalic acid, hexahydrophthalic acid (anhydride), etc.

The polyether polyol may be a polyoxyalkylene-modified polyol obtained by reacting the above-mentioned polyols or dihydroxybenzenes with an alkylene oxide, in addition to the polyalkylene glycol.

The polyester (meth)acrylate oligomer is a compound having an ester bond and at least two (meth)acryloyloxy groups in the molecule. Specifically, it can be obtained by a dehydration condensation reaction of (meth)acrylic acid, polyvalent carboxylic acid or its anhydride, and polyhydric alcohol. As the polyvalent carboxylic acid or its anhydride used in the dehydration condensation reaction, succinic acid (anhydride), adipic acid, maleic acid (anhydride), itaconic acid (anhydride), trimellitic acid (anhydride), Pyromellitic acid (anhydride), hexahydrophthalic acid (anhydride), phthalic acid (anhydride), isophthalic acid, terephthalic acid, etc. In addition, examples of polyhydric alcohols used in the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, Diol, trimethylolethane, trimethylolpropane, di(trimethylol)propane, pentaerythritol, dipentaerythritol, dimethylol heptane, dimethylol propionic acid, dimethylol butyric acid , glycerin, hydrogenated bisphenol A, etc.

The epoxy (meth)acrylate oligomer can be obtained by the addition reaction of polyglycidyl ether and (meth)acrylic acid, and has at least two (meth)acryloyloxy groups in the molecule. Examples of the polyglycidyl ether used in the addition reaction include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bis Phenol A diglycidyl ether, etc.

Among the above (meth)acrylate compounds, the compound having the structure represented by the following formula (XI) or (XII) not only exhibits a high modulus of elasticity in its cured product, but also has a Since a protective layer excellent in the adhesiveness with a polarizing film can be obtained when it is a combination of an alicyclic epoxy type compound, it is preferable.

(In the formula, Q ₁ and Q ₂ independently represent (meth)acryloyloxy or (meth)acryloyloxyalkyl, where the number of carbon atoms in the alkyl group is 1 to 10, and Q ₃ represents hydrogen Or a hydrocarbon group with 1 to 10 carbon atoms.)

In the above formula (XI) or (XII), when Q ₁ or Q ₂ is a (meth)acryloyloxyalkyl group, the alkyl group can be a straight chain or a branched chain, and the number of 1 to 10 can be used. The number of carbon atoms, but generally about 1 to 6 carbon atoms is sufficient. In addition, in formula (XII), when Q ₃ is a hydrocarbon group, it may be a straight chain or a branched chain, typically an alkyl group. As for the alkyl group at this time, generally, about 1 to 6 carbon atoms are sufficient.

The compound represented by the formula (XI) is a di(meth)acrylate derivative of hydrogenated dicyclopentadiene or tricyclodecanedialkonol. As its specific example, it is the substance exemplified previously, and hydrogenated Dicyclopentadienyl di(meth)acrylate [in the formula (XI), Q ₁ =Q ₂ =(meth)acryloyloxy compound], tricyclodecane dimethanol di(meth)acrylic acid Esters [compounds in which Q ₁ =Q ₂ =(meth)acryloyloxymethyl in the formula (XI)] and the like.

In addition, the compound represented by the formula (XII) is a di(meth)acrylate derivative of dioxanediol or dioxanediolkanol, and specific examples thereof are those previously exemplified, including 1,3-dioxane-2,5-diyl di(meth)acrylate [alias: dioxanediol di(meth)acrylate, in formula (XII), Q ₁ =Q ₂ = (Meth)acryloyloxy, compound of Q ₃ =H], acetal compound of hydroxypivalaldehyde and trimethylolpropane [chemical name: 2-(2-hydroxy-1,1-dimethylethane Di(meth)acrylate of -5-ethyl-5-hydroxymethyl-1,3-dioxane] [in formula (XII), Q ₁ =(meth)acryloyloxymethyl group, Q ₂ =2-(meth)acryloyloxy-1,1-dimethylethyl, Q ₃ =ethyl] and the like.

In the curable composition used for forming the first protective layer, the (meth)acrylic compound preferably accounts for 70% by weight or less, more preferably 35 to 70% by weight, of the total active energy ray-curable compound, More preferably, it accounts for 40 to 60% by weight. When content of a (meth)acrylic-type compound exceeds 70 weight%, there exists a tendency for the adhesiveness with a polarizing film to fall.

When the curable composition contains a radical polymerizable compound such as the above-mentioned (meth)acrylic compound, it is preferable to mix a radical polymerization photoinitiator. As the radical polymerization photoinitiator, it is sufficient to start polymerization of radically polymerizable compounds such as (meth)acrylic compounds by irradiation of active energy rays, and conventionally known polymerization initiators can be used. If specific examples of free radical polymerization photoinitiators are given, for example, acetophenone, 3-methylacetophenone, benzil dimethyl ketal, 1-(4-isopropylphenyl)-2 -Hydroxy-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl-2-morpholinopropan-1-one, 2-hydroxy-2-methyl -Acetophenone-based initiators represented by 1-phenylpropan-1-one; diphenyl phenones represented by benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone Methanone-based initiators; benzoin ether-based initiators represented by benzoin propyl ether and benzoin ethyl ether; thioxanthone-based initiators represented by 4-isopropylthioxanthone; other In addition, there are xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, etc.

The compounding quantity of a radical polymerization photoinitiator is 0.5-20 weight part normally with respect to 100 weight part of radical polymerizable compounds, such as a (meth)acrylic-type compound, Preferably it is 1-6 weight part. When the compounding quantity of a radical polymerization photoinitiator is too small, hardening will become inadequate, and there exists a tendency for mechanical strength and the adhesiveness of a protective layer and a polarizing film to fall. Moreover, when the compounding quantity of a radical polymerization photoinitiator is too large, there exists a possibility that the durability performance of the polarizing plate obtained may fall.

The curable composition may further contain a photosensitizer as needed. By using the photosensitizer, the reactivity of cationic polymerization and/or radical polymerization of the active energy ray-curable compound is improved, and the mechanical strength of the protective layer and the adhesiveness between the protective layer and the polarizing film can be improved. Examples of photosensitizers include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halides, photoreducible dyes and the like. Specific photosensitizers include, for example, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α,α-dimethoxy-α-phenylacetophenone; Ketone, 2,4-dichlorobenzophenone, methyl phthaloylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)bis Benzophenone derivatives such as benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; anthracenes such as 2-chloroanthraquinone and 2-methylanthraquinone Quinone derivatives; acridone derivatives such as N-methylacridone and N-butylacridone; in addition, α,α-diethoxyacetophenone, benzil, fluorenone , xanthone, uranyl compounds, halides, etc. These may be used alone or in combination. It is preferable to contain the photosensitizer in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the active energy ray-curable compound.

In addition, the curable composition may contain an antistatic agent for imparting antistatic performance to the polarizing plate. The antistatic agent is not particularly limited, and known antistatic agents can be used. For example, cationic surfactants such as acyl amidopropyl dimethyl hydroxyethyl ammonium nitrate, acyl amidopropyl trimethyl ammonium sulfate, and hexadecylmorpholinium methyl sulfate can be used; Anionic surfactants such as linear alkyl phosphate potassium salt, polyoxyethylene alkyl phosphate potassium salt, and alkane sulfonate; N, N-bis(hydroxyethyl)-N-alkylamine, its fatty acid Nonionic surfactants such as ester derivatives, polyol fatty acid partial esters, and the like. The compounding ratio of these antistatic agents is appropriately determined in accordance with desired characteristics, but it is usually about 0.1 to 20 parts by weight with respect to 100 parts by weight of the active energy ray-curable compound.

Known polymer additives generally used in polymer materials may also be added to the curable composition. For example, primary antioxidants such as phenol-based and amine-based antioxidants, sulfur-based secondary antioxidants, hindered amine-based light stabilizers (HALS), benzophenone-based, benzotriazole-based, benzoic acid UV absorbers such as esters, etc.

In addition, silica fine particles may be added to the curable composition. By adding silica fine particles, the hardness and mechanical strength of the obtained protective layer can be further improved.

Silica fine particles can be mixed with a curable composition in the form of a liquid dispersed in an organic solvent, for example.

The silica fine particles may have reactive functional groups such as hydroxyl groups, epoxy groups, (meth)acryloyl groups, and vinyl groups on the surface thereof. In addition, the particle size of the silica fine particles is usually 100 nm or less, preferably about 5 to 50 nm. When the particle size of the fine particles exceeds 100 nm, an optically transparent protective layer tends not to be obtained.

When using silica fine particles dispersed in an organic solvent, the concentration of the silica is not particularly limited, and commercially available silica of, for example, about 20 to 40% by weight can be used.

As commercially available silica fine particles dispersed in an organic solvent, for example, "methanol silica sol" (manufactured by Nissan Chemical Industries, Ltd., with a silica particle size of 10 to 15nm, solid content 30% by weight), "MA-ST-M" (manufactured by Nissan Chemical Industries, Ltd., silica particle size 20-25nm, solid content 40% by weight), "OSCAL 1132" (Catalytic Chemical Industry ( Co., Ltd., silica particle size 10-20nm, solid content 30-31% by weight); "OSCAL 1232" (manufactured by Catalyst Chemical Industry Co., Ltd., silica particle size 10-20nm, solid content) with ethanol as the organic solvent 30-31% by weight); the organic solvent is n-propanol "OSCAL 1332" (manufactured by Catalyst Chemical Industry Co., Ltd., silica particle size 10-20nm, solid content 30-31% by weight); the organic solvent is iso Propanol "IPA-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10 to 15 nm, solid content 30% by weight), "OSCAL 1432" (manufactured by Catalyst Chemical Industry Co., Ltd., silica grain diameter 10-20nm, solid content 30-31% by weight), organic solvent is n-butanol "NBA-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10-15nm, solid content 20% by weight) , "OSCAL1532" (manufactured by Catalyst Chemical Industry Co., Ltd., silica particle size 10-20 nm, solid content 30-31% by weight), "EG-ST" (Nissan Chemical Industry Co., Ltd.) whose organic solvent is ethylene glycol Co., Ltd., silica particle size 10-15nm, solid content 20% by weight); "OSCAL 1632" (manufactured by Catalyst Chemical Industry Co., Ltd., silica particle size 10-20nm, solid content) with ethyl cellosolve as the organic solvent Components 30-31% by weight); the organic solvent is ethylene glycol mono-n-propyl ether "NPC-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10-15nm, solid content 30% by weight); "DMAC-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10 to 15 nm, solid content 20% by weight) in which the organic solvent is dimethylacetamide, "DMAC-ST-ZL" (Nissan Chemical Industry Co., Ltd. Co., Ltd., silica particle size 70-100nm, solid content 20% by weight); "XBA-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle diameter 10-15nm, solid content 30% by weight); organic solvent is methyl isobutyl ketone "MIBK-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10-15nm, solid content 30% by weight) ); "MEK-ST" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10-15 nm, solid content 30% by weight) and "SP-1120" (Konishi Chemical Industry Co., Ltd.) in which the organic solvent is methyl ethyl ketone Co., Ltd., carbon dioxide Silica particle size 15-20nm, solid content 5-10% by weight), "SP-6120" (manufactured by Konishi Chemical Industry Co., Ltd., silica particle size 15-20nm, solid content 5-10% by weight), etc., can One or more of these are used appropriately. In addition, "Snotex 20" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10-20 nm) and "Snotex C" (manufactured by Nissan Chemical Industry Co., Ltd., silica particle size 10~20nm), etc.

The silica fine particles are preferably added in an amount of 5 to 250 parts by weight, more preferably 10 to 100 parts by weight, based on 100 parts by weight of the active energy ray-curable compound contained in the curable composition. When the amount of silica fine particles added is too small, the increase in hardness of the protective layer due to the addition of silica fine particles may not be sufficient. On the other hand, when the addition amount of silica fine particles is too large, the adhesiveness of a polarizing film and a protective layer may fall. Also, when the amount of silica fine particles added is too large, the dispersion stability of the fine particles in the curable composition may decrease, and the viscosity of the curable composition may increase too much.

Furthermore, the curable composition may contain a solvent as needed. The solvent can be appropriately selected according to the solubility of the components constituting the curable composition. Commonly used solvents include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol, propanol, isopropanol, and n-butanol. ; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate; methyl cellosolve, ethyl cellosolve Cellosolves such as agent and butyl cellosolve; Halogenated hydrocarbons such as methylene chloride and chloroform, etc. The blending ratio of the solvent is appropriately selected from the viewpoint of desired viscosity of the curable composition in consideration of processability such as film-forming properties.

Moreover, a curable composition may contain a leveling agent as needed. When the curable composition is coated on a polarizing film or a base material, when the wettability of the polarizing film or the base material is insufficient, or the cured product of the curable composition has poor surface properties, it may be Improve by adding leveling agent. As the leveling agent, various compounds such as silicone-based, fluorine-based, polyether-based, acrylic copolymer-based, titanate-based, and the like can be used. These leveling agents may be used alone or in combination of two or more.

The leveling agent is preferably added in an amount of 0.01 to 1 part by weight, more preferably 0.1 to 0.7 parts by weight, and still more preferably 0.2 to 0.5 parts by weight, based on 100 parts by weight of the active energy ray-curable compound contained in the curable composition. When the added amount of the leveling agent is too small, the improvement of wettability and surface properties may not be sufficient. On the other hand, when the addition amount of a leveling agent is too much, the adhesiveness of a polarizing film and a protective layer may fall.

The thickness of the first protective layer formed from the curable composition containing the active energy ray-curable compound described above is preferably 0.1 to 10 μm, more preferably 1 to 5 μm. When the thickness of the first protective layer is too thin, the durability becomes insufficient, and when it is too thick, the effect of thinning and reducing the weight of the polarizing plate decreases. The method of forming the first protective layer using the curable composition will be described later.

(2) Second protective layer

A second protective layer formed of a thermoplastic resin film is laminated on the surface of the polarizing film opposite to the side on which the first protective layer is laminated via an adhesive layer. As the second protective layer in the polarizing plate of the present invention, for example, a thermoplastic resin film composed of an appropriate material that has been widely used as a forming material of the protective layer in the art such as Examples include cellulose acetate-based resins, cycloolefin-based resins, polyolefin-based resins, acrylic resins, polyimide-based resins, polycarbonate-based resins, polyester-based resins, and the like. From the viewpoint of mass productivity and adhesiveness, among the above, it is preferable to use a cellulose acetate-based resin film or a cycloolefin-based resin film as the second protective layer. In addition, it is more preferable to use a cellulose acetate-based resin film as the second protective layer from the viewpoint of easiness of providing a surface treatment layer and optical properties.

Cycloolefin-based resins suitable for use in the second protective layer of the present invention are, for example, thermoplastic resins having monomer units composed of cyclic olefins (cycloolefins) such as norbornene and polycyclic norbornene-based monomers. (Also known as thermoplastic cycloolefin resin). The cyclic olefin-based resin may be a ring-opening polymer of the above-mentioned cyclic olefin, a hydrogenated product of a ring-opening polymer using two or more kinds of cyclic olefins, or an aromatic compound having a cyclic olefin, a chain olefin, or a vinyl group. Addition polymers of compounds, etc. In addition, it is also effective to introduce a polar group.

When using a cyclic olefin, a chain olefin, and a copolymer of an aromatic compound having a vinyl group to form the second protective layer, the chain olefin includes ethylene, propylene, etc., and the aromatic compound having a vinyl group can be Examples thereof include styrene, α-methylstyrene, and nuclear alkyl (nuclear alkyl)-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). In particular, when a terpolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group is used to constitute the second protective layer, the amount of monomer units composed of cycloolefin can be relatively small as described above. In this terpolymer, the monomer unit consisting of a chain olefin is usually 5 to 80 mol%, and the monomer unit consisting of an aromatic compound having a vinyl group is usually 5 to 80 mol%.

As the cycloolefin-based resin, suitable commercially available products can be used, for example, "Topas" (manufactured by Ticona Co., Ltd.), "ARTON" (manufactured by JSR Co., Ltd.), "ZEONOR" (manufactured by Japan ZEON Co., Ltd.), "ZEONEX " (manufactured by Japan Zeon Co., Ltd.), "APEL" (manufactured by Mitsui Chemicals Co., Ltd.) (the above are all trade names), etc. When forming such a cycloolefin-based resin into a film to obtain a film, known methods such as a solvent casting method and a melt extrusion method can be appropriately used. In addition, for example, "Escina" (manufactured by Sekisui Chemical Co., Ltd.), "SCA40" (manufactured by Sekisui Chemical Co., Ltd.), "Zeonor Film" (manufactured by Optes Co., Ltd.) and the like can also be prepared in advance. A commercially available cycloolefin-based resin film-formed product was used as the second protective layer.

The cycloolefin-based resin film used as the second protective layer may be uniaxially stretched or biaxially stretched. The draw ratio at this time is usually 1.1 to 5 times, preferably 1.1 to 3 times.

In addition, the cellulose acetate-based resin film suitable for use as the second protective layer in the present invention is a film composed of a part or all of cellulose acetate, for example, triacetyl cellulose film, diacetyl cellulose film, etc. Plain film etc.

As the cellulose acetate-based resin constituting such a cellulose acetate-based resin film, suitable commercially available products such as "FUJITAC TD80" (manufactured by Fuji Photo-Film Co., Ltd.), "FUJITAC TD80UF" (manufactured by Fuji Photo-Film Co., Ltd.) can be used appropriately. cellulose acetate), "FUJITACTD80UZ" (manufactured by Fuji Photo-Film Co., Ltd.), "KC8UX2M" (manufactured by KONICA MINOLTA OPTO Co., Ltd.), "KC8UY" (manufactured by KONICA MINOLTA OPTO Co., Ltd.), etc. It is a film made of resin.

The second protective layer used in the polarizing plate of the present invention preferably has a small thickness, but if it is too thin, the strength tends to decrease and the processability tends to be poor, and if it is too thick, the transparency decreases or the weight of the polarizing plate increases. the trend of. From this point of view, the thickness of the second protective layer in the polarizer of the present invention is usually 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm in the case of a protective layer made of a cycloolefin resin. , and when the protective layer is made of cellulose acetate resin, it is usually 20 to 200 μm, preferably 30 to 150 μm, and more preferably 40 to 100 μm.

The second protective layer in the polarizing plate of the present invention may be obtained by performing surface treatment such as anti-glare treatment, hard-coat treatment, antistatic treatment, and anti-reflection treatment on the surface opposite to the surface to which the polarizing film is pasted. layer. In addition, a coating layer composed of a liquid crystal compound, a high molecular weight compound thereof, or the like may be formed on the surface of the second protective layer opposite to the surface to which the polarizing film is attached.

The polarizing film and the second protective layer (thermoplastic resin film) are pasted using the adhesive described in detail below. When using an adhesive to attach these films, in order to improve the adhesiveness, it is also possible to appropriately implement plasma treatment, corona treatment, and ultraviolet irradiation on the bonding surface of the polarizing film and/or the second protective layer attached to it. Treatment, flame treatment, saponification treatment and other surface treatments. As a saponification process, the method of immersing in alkali aqueous solution, such as sodium hydroxide and potassium hydroxide, is mentioned. Hereinafter, the adhesive agent used for bonding a polarizing film and a 2nd protective layer is demonstrated.

(adhesive layer)

The adhesive layer included in the polarizing plate of the present invention is a layer composed of an adhesive (adhesive composition) or a cured product thereof used when bonding the polarizing film and the second protective layer. The adhesive composition of the present invention is not particularly limited, but examples include curable compositions containing an active energy ray-curable compound, those obtained by dissolving the adhesive component in water, or those obtained by dispersing the adhesive component in water. water-based adhesives. Among them, it is preferable to use a curable composition containing an active energy ray-curable compound from the viewpoint of not requiring a drying step.

As the curable composition as the above-mentioned adhesive composition, the same composition as the curable composition for forming the above-mentioned first protective layer can be mentioned. The curable composition forming the first protective layer and the active energy ray-curable compound contained therein may be the same as the curable composition serving as the adhesive composition and the active energy ray-curable compound contained therein. Can be different.

In addition, examples of water-based adhesives obtained by dissolving the adhesive component in water or dispersing the adhesive component in water include adhesive compositions using polyvinyl alcohol-based resins and polyurethane resins as main components.

When polyvinyl alcohol-based resin is used as the main component of the water-based adhesive composition, the polyvinyl alcohol-based resin includes, in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl Modified polyvinyl alcohol-based resins such as radical-modified polyvinyl alcohol, methylol-modified polyvinyl alcohol, and amino-modified polyvinyl alcohol. When a polyvinyl alcohol-based resin is used as an adhesive component, the adhesive is often prepared from an aqueous solution of the polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of water.

In an adhesive containing a polyvinyl alcohol-based resin as a main component, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent in order to improve the adhesiveness. Examples of water-soluble epoxy resins include polyamide polyamine epoxy resins obtained by reacting epichlorohydrin with polyamide polyamines obtained by passing diethylenetriamine, triethylene It is obtained by the reaction of polyalkylene polyamines such as tetramine and dicarboxylic acids such as adipic acid. Commercially available polyamide polyamine epoxy resins include "Sumirez Resin 650" and "Sumirez Resin 675" sold by Sumika Chemtex Co., Ltd., "WS-525" sold by Japan PMC Co., Ltd., These commercially available items can be preferably used. The addition amount of these curable components or a crosslinking agent is 1-100 weight part normally with respect to 100 weight part of polyvinyl-alcohol-type resins, Preferably it is 1-50 weight part. When the added amount is small, the adhesiveness-improving effect is reduced, and on the other hand, when the added amount is large, the adhesive bond layer tends to become brittle.

When a polyurethane resin is used as the main component of the water-based adhesive, an example of a suitable adhesive composition includes a mixture of a polyester-based ionomer type polyurethane resin and a compound having a glycidyloxy group. The polyester-based ionomer type polyurethane resin referred to here is a polyurethane resin having a polyester skeleton into which a small amount of ionic components (hydrophilic components) are introduced. Since this ionomer type polyurethane resin is directly emulsified in water to form an emulsion without using an emulsifier, it is preferable as a water-based adhesive. Polyester-based ionomer type polyurethane resins are known per se. For example, in JP-A No. 7-97504, a polyester-based ionomer type polyurethane resin is described as an example of a polymer dispersant for dispersing a phenolic resin in an aqueous medium, and JP-A 2005-070140 Publication No. 2005-181817 and Japanese Patent Application Laid-Open No. 2005-181817 disclose a mixture of a polyester-based ionomer polyurethane resin and a compound having a glycidyloxyl group as an adhesive to bond a cycloolefin-based resin film to a polyvinyl alcohol-based The form on the polarizing film made of resin.

The thickness of the adhesive layer of the present invention is preferably 20 μm or less, more preferably 10 μm or less, and still more preferably 5 μm or less. When the thickness of the adhesive layer is thin, there is little possibility of impairing the appearance of the polarizing plate.

(adhesive layer)

In addition, the polarizing plate of the present invention may have an adhesive layer on the surface of the first protective layer opposite to the polarizing film side. This adhesive layer can be used, for example, when bonding with a liquid crystal cell. When the adhesive layer is used to bond the polarizing plate and the liquid crystal cell to form a liquid crystal display device, the protective layer present between the polarizing film and the liquid crystal cell is composed of a cured product of a curable composition and is in-plane and The retardation in the film thickness direction of the first protective layer is approximately zero, so it can effectively prevent light leakage during black display.

The formation of the adhesive layer can be carried out, for example, by dissolving or dispersing an adhesive composition such as a base polymer serving as an adhesive component in an organic solvent such as toluene or ethyl acetate. 10% to 40% by weight solution, which is directly coated on the first protective layer to form an adhesive layer; an adhesive layer is formed on the protective film in advance, and it is transferred to the first protective layer to form an adhesive layer. The way of the mixture layer, etc. The thickness of the pressure-sensitive adhesive layer is determined according to its adhesive force and the like, but is usually in the range of 1 to 50 μm.

Examples of the base polymer include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers and the like. Among them, it is preferable to select and use an adhesive such as an acrylic adhesive using an acrylic polymer as a raw material polymer, that is, it has excellent optical transparency, maintains moderate wettability, cohesion, and is compatible with the first protective layer and the liquid crystal cell. It is an adhesive that has excellent adhesiveness, weather resistance, heat resistance, etc., and does not cause peeling problems such as floating and peeling under conditions of heating and humidification.

Examples of the acrylic base polymer contained in the acrylic adhesive include alkyl esters of acrylic acid having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, and a butyl group, and (meth)acrylic acid, Acrylic copolymers of functional group-containing acrylic monomers such as hydroxyethyl (meth)acrylate. The glass transition temperature of the acrylic copolymer is preferably 25°C or lower, more preferably 0°C or lower. Moreover, it is preferable that the weight average molecular weight of this acrylic-type copolymer is 100,000 or more.

Fillers, pigments, colorants, antioxidants, ultraviolet absorbers, etc., which are composed of inorganic powders such as glass fibers, glass beads, resin beads, and metal powders, etc., may also be blended into the adhesive layer as needed. Examples of ultraviolet absorbers include salicylate-based compounds, benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like.

<Manufacturing method of polarizing plate>

The polarizing plate of the present invention can be produced through the following steps. The order of the following steps (i) and (ii) is not particularly limited, and may be performed simultaneously.

(i) a step of forming the above-mentioned first protective layer on one surface of the polarizing film, and

(ii) A step of attaching the above-mentioned second protective layer to the other surface of the polarizing film via an adhesive.

In the above step (i), examples of the method for forming the first protective layer include the following methods. First, a curable composition containing an active energy ray-curable compound to form a first protective layer is applied on a base material, dried if necessary, and a coating layer (coating layer) of the curable composition is provided on the surface of the base material. forming process). Then, the polarizing film and the coating layer are bonded together using the coated surface as a bonding surface (coating layer bonding step). Next, for the laminate composed of the polarizing film/coating layer/substrate (when the step (ii) is performed prior to the step (i), the laminate also contains an adhesive layer and a second protective layer), for example, from the substrate The material side is irradiated with active energy rays such as visible rays, ultraviolet rays, X-rays, and electron rays or heated to cure the coating layer made of the curable composition to form the first protective layer (curing step). Finally, the substrate on the first protective layer is removed (substrate removal step). Here, examples of substrates include metal tapes, glass plates, polyethylene terephthalate films, polycarbonate films, triacetyl cellulose films, norbornene films, polyester films, polystyrene films, etc. film etc. The surface of the substrate on which the curable composition is applied may be subjected to, for example, a peeling treatment.

In addition, as another method of the above-mentioned step (i), directly coating a curable composition containing an active energy ray-curable compound for forming the first protective layer on a polarizing film, irradiating active energy rays or heating, Thereby, the coating layer which consists of a curable composition is cured, and the method of forming a 1st protective layer. In this case, the base material may not be required.

In the above-mentioned step (ii), as a method of bonding the second protective layer, the following methods can be mentioned. First, the adhesive composition is applied on the second protective layer (thermoplastic resin film), and dried if necessary. Next, the polarizing film and the second protective layer are bonded together using the applied surface as a bonding surface (film bonding step). Then, make the laminate composed of the polarizing film/adhesive/second protective layer (when the step (i) is performed before the step (ii), the laminate also contains the first protective layer (or the coating of the curable composition) Cloth layer) and substrate) are dried, or the laminate is irradiated with active energy rays such as visible rays, ultraviolet rays, X-rays, and electron rays or heated, thereby curing the adhesive composition, thereby making the polarizing film and the second protective layer Bond, allow to dry as needed. When a curable composition containing an active energy ray-curable compound is used as an adhesive composition, since a drying step can be omitted, the production efficiency can be improved.

In addition, the method of directly coating the adhesive composition on the polarizing film, pasting the second protective layer, drying the adhesive composition, or irradiating active energy rays or heating to cure the adhesive composition, thereby polarizing the film. The film and the second protective layer are glued and dried as needed.

It is also possible to form the first protective layer and the second protective layer simultaneously. For example, as an adhesive, a curable adhesive composition (a curable composition containing an active energy ray-curable compound, a water-based adhesive containing a curable component or a crosslinking agent, etc.) is used to form a second protective layer/adhesive/ After forming a laminate composed of polarizing film/coating layer/substrate, the laminate is irradiated with active energy rays or heated, for example, from the substrate side to simultaneously cure the adhesive and the coating layer to obtain a polarizing plate. According to this method, the curing step is completed at one time, so that further improvement in manufacturing efficiency can be achieved.

In the present invention, the coating method of the curable composition containing an active energy ray-curable compound and the adhesive composition for forming the first protective layer is not particularly limited, and for example, a doctor blade, a wire bar, a die coater, a Various coating methods such as dot coater and gravure coater. In addition, metal, rubber, etc. can be used as the material of the roller in the method of dripping the above-mentioned active energy ray-curable compound-containing curing process between the polarizing film and the second protective layer or the base material. A method of spreading the adhesive composition or adhesive composition evenly by applying pressure with a roller or the like. In addition, those rollers may be made of the same material or different materials in the method described below in which the above-mentioned active energy ray-containing material is dropped between the polarizing film and the second protective layer or the base A method in which a curable composition of a curable compound or an adhesive composition is spread by applying pressure between rollers.

When curing the curable composition containing an active energy ray-curable compound and/or the adhesive composition that forms the first protective layer by irradiation with active energy rays, the light source used is not particularly limited, but can be used in Those with luminescence distribution below 400nm include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

The light irradiation intensity to the curable composition and the adhesive composition can vary according to each composition, and the irradiation intensity in the effective wavelength region for the activation of the radical polymerization photoinitiator and/or cationic polymerization photoinitiator is preferably 10 ~2500mW/cm ² . When the light irradiation intensity to the curable composition is less than 10mW/ ^cm2 , the reaction time is too long ^. Heat may cause yellowing of the curable composition and adhesive composition, and deterioration of the polarizing film. The light irradiation time of the curable composition and the adhesive composition is controlled according to each composition, and it is not particularly limited, but it is preferably set so that the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 2500 mJ/cm ² . When the cumulative amount of light applied to the curable composition or adhesive composition is less than 10 mJ/cm ² , generation of active species derived from the polymerization initiator is insufficient, and the resulting protective layer or adhesive layer may be insufficiently cured. On the other hand, when the cumulative light quantity exceeds 2500 mJ/cm ² , the irradiation time becomes very long, which is disadvantageous in improving productivity. In addition, the irradiation of active energy rays is preferably carried out within a range in which various properties such as polarization degree and transmittance of the polarizing film do not decrease.

<Liquid crystal display device>

The liquid crystal display device of the present invention is provided with the above-mentioned polarizing plate of the present invention, more specifically, a liquid crystal cell and a pair of polarizing plates arranged on both sides of the liquid crystal cell, and either or both of the polarizing plates is the above-mentioned polarizing plate of the present invention. Invented polarizers for liquid crystal display devices. Here, in the liquid crystal display device of the present invention, the polarizing plate of the present invention is bonded to the liquid crystal cell so that the first protective layer is on the liquid crystal cell side. That is, when the above-mentioned pressure-sensitive adhesive layer is provided on the first protective layer, it is bonded to the liquid crystal cell via the pressure-sensitive adhesive layer. The liquid crystal display device of the present invention having such a structure not only effectively prevents light leakage during black display, but also realizes thinness and weight reduction.

The liquid crystal cell used in the liquid crystal display device of the present invention may be of any type, and when an IPS mode liquid crystal cell operating in the in-plane switching mode is used, a remarkable effect of preventing light leakage during black display can be obtained particularly.

Example

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" indicating usage-amount or content are based on weight unless otherwise specified.

(Manufacturing example 1: Production of polarizing film)

An aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.02/2/100 at 30°C after immersing a polyvinyl alcohol film with an average degree of polymerization of about 2400, a degree of saponification of 99.9 mol% or more, and a thickness of 75 μm in pure water at 30°C Dip in. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 12/5/100 at 56.5°C. Next, after washing with 8° C. pure water, it was dried at 65° C. to obtain a polarizing film in which iodine was adsorbed on polyvinyl alcohol and iodine was oriented. Stretching is mainly carried out in the process of iodine dyeing and boric acid treatment, and the total stretching ratio is 5.3 times.

(Manufacturing Example 2: Preparation of Curable Composition I)

First, the following components were mixed to obtain curable composition I.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (manufactured by Daicel Chemical Co., Ltd., Ceroxide 2021P) 35 parts

Bis(3-ethyl-3-oxetanylmethyl) ether (manufactured by Toyasei Co., Ltd., ARONOXETANE OXT-221) 15 parts

Diacrylate of acetal compound of hydroxypivalaldehyde and trimethylolpropane (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., A-DOG) 50 parts

2-Hydroxy-2-methyl-1-phenylpropan-1-one (manufactured by Ciba Specialty Chemicals Co., Ltd., DAROCURE1173, free radical polymerization photoinitiator) 2.5 parts

4,4'-bis[diphenylsulfonium]diphenylsulfide bishexafluorophosphate cationic polymerization photoinitiator (UVACURE 1590 manufactured by DAICEL-CYTEC Co., Ltd.) 2.5 parts

Silicone leveling agent (manufactured by Dow Corning Toray, SH710) 0.2 parts

In addition, the above-mentioned A-DOG (diacrylate ester of an acetal compound of hydroxypivalaldehyde and trimethylolpropane) is a compound having the following structure.

(Manufacturing example 3: Preparation of curable composition II)

The following components were mixed to obtain curable composition II.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (manufactured by Daicel Chemical Co., Ltd., Ceroxide 2021P) 75 parts

Bis(3-ethyl-3-oxetanylmethyl) ether (manufactured by Toyasei Co., Ltd., ARONOXETANE OXT-221) 25 parts

4,4'-bis[diphenylsulfonium]diphenylsulfide bishexafluorophosphate cationic polymerization photoinitiator (UVACURE 1590 manufactured by DAICEL-CYTEC Co., Ltd.) 5 parts

Silicone leveling agent (manufactured by Dow Corning Toray, SH710) 0.2 parts

(Manufacturing Example 4: Preparation of polyvinyl alcohol-based adhesive)

The following components were mixed to obtain a polyvinyl alcohol-based adhesive.

Pure water 100 parts

Carboxyl-modified polyvinyl alcohol (“Kuraray Poval KL 318” manufactured by Kuraray Co., Ltd.)

1.8 copies

Water-soluble polyamide epoxy resin ("Sumirez Resin 650" manufactured by Sumika Chemtex Co., Ltd.) (aqueous solution with a solid content concentration of 30%) 0.9 parts

(Manufacturing Example 5: Production of Polarizing Plate A)

On one side of the polarizing film prepared in Production Example 1, the polyvinyl alcohol-based adhesive obtained in Production Example 4 was coated, and a protective layer composed of saponified triacetyl cellulose (KONICA MINOLTA OPTO Co., Ltd. ) system, KC8UY, thickness 80μm). This was dried at 60 degreeC for 6 minutes, and the polarizing plate A which has a protective layer on one surface was produced.

<Example 1>

Coat one side of a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., ESTER FILM E5100) using a coater (BAR COATER, manufactured by Daiichi Rika Co., Ltd.) Curable composition I obtained in Production Example 2. In addition, a corona discharge treatment was applied to one side of a protective layer (manufactured by KONICA MINOLTA OPTO Co., Ltd., KC8UY, thickness 80 μm) composed of a triacetyl cellulose film not subjected to saponification treatment, and the surface was similarly coated and cured. Sexual Composition II. At this time, since the film thickness of the coating layer when the curable composition is applied changes according to the viscosity, the film thickness is adjusted by changing the type of bar of the bar coater. Next, using a sticking device (manufactured by FUJIPLA Co., Ltd., LPA3301), the PET film having the coating layer of the above-mentioned curable composition I is pasted so that the respective coating layer sides become the bonding surface with the polarizing film. One surface of the polarizing film produced in Production Example 1 was combined, and the protective layer having the coating layer of the above-mentioned curable composition II was bonded to the other surface.

Using D VALVE manufactured by Fusion UV Systems Co., Ltd., the laminated product was irradiated with ultraviolet light at a cumulative light intensity of 1500 mJ/cm ² from the PET film side, and the coating layers of curable compositions I and II arranged on both sides of the polarizing film solidify. Then, the PET film is peeled off, and a transparent first protective layer (cured product of curable composition 1) is set on one side of the polarizing film and a transparent second protective layer (triacetyl cellulose) is set on the other side. film) polarizer. Moreover, when the thickness of this polarizing plate was measured using a film thickness measuring device (made by Nikon Corporation, ZC-101), it was 116 micrometers. In addition, the thickness of the first protective layer was 4 μm.

<Example 2>

Coat one side of a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., ESTER FILM E5100) using a coater (BAR COATER, manufactured by Daiichi Rika Co., Ltd.) Curable composition I obtained in Production Example 2. At this time, since the film thickness of the coating layer at the time of coating a curable composition changes with viscosity, the film thickness was adjusted by changing the rod model of a bar coater. Next, the PET film having the coating layer of the above-mentioned curable composition I was bonded to the polarizing film using a bonding device (manufactured by FUJIPLA Co., Ltd., LPA3301) so that the coating layer side becomes the bonding surface with the polarizing film. On the opposite side of the surface to which the protective layer was bonded of the polarizing plate A produced in manufacture example 5.

The bonded product was irradiated with ultraviolet rays from the PET film side at a cumulative light intensity of 1500 mJ/cm ² using a D VALVE manufactured by Fusion UV Systems to cure the coating layer of the curable composition I placed on the polarizing film. Then, the PET film was peeled off to produce a polarizing plate. In addition, the thickness of this polarizing plate was 114 μm. In addition, the thickness of the first protective layer (cured product of curable composition I) was 4 μm.

<Comparative example 1>

The polarizing plate A produced in Production Example 5 was used. The thickness of the polarizing plate A was 110 μm.

<Comparative example 2>

On both sides of the polarizing film made in Production Example 1, the polyvinyl alcohol-based adhesive agent obtained in Production Example 4 was coated, and on one side, a protective layer composed of saponified triacetyl cellulose ( KONICA MINOLTA OPTO Co., Ltd., KC8UY, thickness 80 μm), and on the other surface, a protective layer composed of triacetyl cellulose and having an in-plane retardation Re _and a retardation R _th in the film thickness direction of approximately 0 (KONICA Minolta Opto Co., Ltd. product, KC4UEW, thickness 40 μm). This was dried at 60° C. for 6 minutes to produce a polarizing plate. The thickness of the polarizing plate was 150 μm.

<Evaluation test>

(1) Adhesion durability test

After the pressure-sensitive adhesive layer was provided on the polarizing plates of Examples 1-2 and Comparative Examples 1-2 by the following method, the durability of the polarizing plate was evaluated according to the following test method.

[Formation of Adhesive Layer]

The adhesive solution containing the copolymer of butyl acrylate and acrylic acid, urethane acrylate oligomer, isocyanate crosslinking agent and organic solvent is coated on the first protective layer of the polarizer of embodiment 1 and 2. layer, on the polarizing film of the polarizing plate of Comparative Example 1, and on the protective layer (KC4UEW) made of triacetylcellulose of the polarizing plate of Comparative Example 2, by drying it, an adhesive layer was formed on each polarizing plate .

[experiment method]

After bonding the polarizing plate with an adhesive layer to glass via the adhesive layer, a heat resistance test was performed for 300 hours of storage under dry conditions at a temperature of 80° C., and the polarizing plate after the test was visually observed. The results are shown in Table 1. The evaluation criteria are as follows.

◯: Changes in appearance such as floating, peeling, and foaming were hardly observed.

Δ: Appearance changes such as floating, peeling, and foaming are slightly noticeable.

×: Appearance changes such as floating, peeling, and foaming are clearly recognized.

(2) Determination of delay of protective layer

The first protective layer (cured product of curable composition 1) used in the polarizers of Examples 1 and 2 and the protective layer (KC4UEW) made of triacetylcellulose of the polarizer of Comparative Example 2 were measured by the following method. In-plane retardation Re and retardation _{R th in} the film thickness direction. The results are shown in Table 1. In addition, the measurement results of the retardation of the first protective layer used in the polarizers of Examples 1 and 2 are cured compositions obtained by forming a cured product of the curable composition I on a PET film and peeling the PET film as described above. The result of the object film (thickness 4μm).

[in-plane delay R _e ]

Using a measuring machine "KOBRA-21ADH" manufactured by Oji Scientific Instruments Co., Ltd., the in-plane retardation _Re was measured by the rotating analyzer method with monochromatic light having a wavelength of 559 nm.

[Retardation R _th in film thickness direction]

The retardation R _th in the film thickness direction was measured with monochromatic light having a wavelength of 559 nm using the same "KOBRA-21ADH" as above. The measurement procedure of this measuring machine is as follows. Using the in-plane retardation R _e , the retardation R ₄₀ measured at an inclination of 40 degrees with the slow axis as the tilt axis, the thickness d of the film, and the average refractive index n ₀ of the film, the following formula (3) to (5) n _x , _ny and _nz are obtained, and they are substituted into the above formula (2) to calculate the retardation R _th in the film thickness direction.

R _e =(n _x -n _y )×d (3)

R ₄₀ ＝(n _x -n _y ')×d/cos(φ) (4)

(n _x +n _y +n _z )/3=n ₀ (5)

here,

φ＝sin ^-1 [sin(40°)/n ₀ ]

n _y '＝n _y ×n ₀ /[n _y ² ×sin ² (φ)+n _z ² ×cos ² (φ)] ^1/2

Table 1

It should be understood that the embodiments and examples disclosed this time are illustrative in all points and not limited thereto. The scope of the present invention is shown not by the above-mentioned description but by the claims of the present invention, and all changes within the meanings equivalent to the claims of the present invention and within the scope are included.

Claims (15)

1. A polarizer, characterized in that it has: A polarizing film in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film and the dichroic dye is oriented, a first protective layer laminated on one surface of the polarizing film and composed of a cured product of a curable composition containing an active energy ray curable compound; and A second protective layer formed of a thermoplastic resin film is laminated on the other surface of the polarizing film via an adhesive layer. 2. The polarizing plate according to claim 1, characterized in that, The curable composition contains an epoxy-based compound having at least one epoxy group in a molecule as the active energy ray-curable compound. 3. The polarizing plate according to claim 2, characterized in that, The epoxy-based compound has at least one epoxy group bonded to an alicyclic ring. 4. The polarizing plate according to claim 2 or 3, characterized in that, The curable composition further contains an oxetane compound as the active energy ray curable compound. 5. The polarizing plate according to any one of claims 2 to 4, characterized in that: The curable composition further contains a (meth)acrylic compound having at least one (meth)acryloyloxy group in a molecule as the active energy ray-curable compound. 6. The polarizing plate according to any one of claims 1 to 5, characterized in that: The thickness of the first protective layer is 0.1-10 μm. 7. The polarizing plate according to any one of claims 1 to 6, characterized in that: The second protective layer is formed of a cellulose acetate resin film. 8. The polarizing plate according to any one of claims 1 to 7, characterized in that: The adhesive layer is composed of a cured product of a curable composition containing an active energy ray curable compound. 9. The polarizing plate according to any one of claims 1 to 8, characterized in that, An adhesive layer is further laminated on the surface of the first protective layer opposite to the polarizing film side. 10. The polarizing plate according to any one of claims 1 to 9, characterized in that: Used in liquid crystal display devices operating in in-plane switching mode. 11. A liquid crystal display device, characterized in that, A liquid crystal cell and a pair of polarizers arranged on both sides of the liquid crystal cell are provided, At least one of the pair of polarizers is the polarizer according to claim 9, and is bonded to the liquid crystal cell via its adhesive layer. 12. A liquid crystal display device, characterized in that, A liquid crystal cell and a pair of polarizers arranged on both sides of the liquid crystal cell are provided, The pair of polarizers are both polarizers according to claim 9, and are bonded to the liquid crystal cell by means of their adhesive layers. 13. The liquid crystal display device according to claim 11 or 12, characterized in that: The liquid crystal cell has two substrates and a liquid crystal layer sandwiched between the substrates and aligned substantially parallel to the substrates in a state where no voltage is applied, and operates in an in-plane switching mode. 14. A method of manufacturing a polarizer, characterized in that: The polarizer includes: a polarizing film in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film and the dichroic dye is oriented; A first protective layer composed of a cured product of a curable composition of a polarizing compound; and a second protective layer formed of a thermoplastic resin film laminated on the other side of the polarizing film via an adhesive layer; The manufacturing method includes: A coating layer forming step of providing a coating layer of the curable composition on the surface of the substrate, a coating layer bonding step of bonding the coating layer of the curable composition provided on the surface of the substrate to one surface of the polarizing film, a film bonding process of bonding the second protective layer on the other surface of the polarizing film by means of an adhesive, a curing step of curing the coating layer and the adhesive; and A substrate removal step of removing the substrate. 15. The method for manufacturing a polarizing plate according to claim 14, wherein: In the curing step, the coating layer and the adhesive are cured simultaneously by irradiating active energy rays from the substrate side.

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